How does El Niño influence global climate?
El Niño is the ENSO phase in which central and eastern tropical Pacific surface waters become unusually warm and atmospheric circulation shifts.
Formation process and geographic mechanism
Normally trade winds push warm water west and cold nutrient-rich water rises in the eastern Pacific. During El Niño trades may weaken, warm water spreads east and upwelling declines. Shifting tropical rainfall alters upper-atmosphere waves. These teleconnections change seasonal probabilities of rain, temperature, drought and storms in various regions.
Spatial outcomes, measurement and management
El Niño events differ in strength and pattern; warming location, season and other oscillations modify outcomes. It cannot be named as the sole cause of one storm in a city, but it can shift probability distributions. Reduced upwelling affects marine ecosystems. Forecasts combine buoys, satellites and coupled ocean-atmosphere models.